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Field and laboratory studies were conducted in April and November 2003 to provide the first direct measurements of the benthic flux of dissolved mercury species (total and methylated forms) between the bottom sediment and water column at two sampling locations within the southern component of San Francisco Bay, California (hereafter referred to as South Bay): one within the main channel and the other in the western shoal area. Because of interest in the effects of historic mercury mining within watersheds that drain into South Bay, the solutes of primary interest were dissolved-mercury species and the predominant ligands that often control mercury speciation (dissolved sulfide and dissolved organic carbon). Benthic...
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In the late 1800s, mills in the Washoe Lake area, Nevada, used elemental mercury to remove gold and silver from the ores of the Comstock deposit. Since that time, mercury contaminated waste has been distributed from Washoe Lake, down Steamboat Creek, and to the Truckee River. The creek has high mercury concentrations in both water and sediments, and continues to be a constant source of mercury to the Truckee River. The objective of this study was to determine concentrations of total and methyl mercury (MeHg) in surface sediments and characterize their spatial distribution in the Steamboat Creek watershed. Total mercury concentrations measured in channel and bank sediments did not decrease downstream, indicating...
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The restoration of 18 acres of historic tidal marsh at Crissy Field has had great success in terms of public outreach and visibility, but less success in terms of revegetated marsh sustainability. Native cordgrass (Spartina foliosa) has experienced dieback and has failed to recolonize following extended flooding events during unintended periodic closures of its inlet channel, which inhibits daily tidal flushing. We examined the biogeochemical impacts of these impoundment events on plant physiology and on sulfur and mercury chemistry to help the National Park Service land managers determine the relative influence of these inlet closures on marsh function. In this comparative study, we examined key pools of sulfur,...
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Millions of pounds of mercury (Hg) were deposited in the river and stream channels of the Sierra Nevada from placer and hard-rock mining operations in the late 1800s and early 1900s. The resulting contaminated sediments are relatively harmless when buried and isolated from the overlying aquatic environment. The entrained Hg in the sediment constitutes a potential risk to human and ecosystem health should it be reintroduced to the actively cycling portion of the aquatic system, where it can become methylated and subsequently bioaccumulated in the food web. Each year, sediment is mobilized within these fluvial systems during high stormflows, transporting hundreds of tons of Hg-laden sediment downstream. The State...
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Field and laboratory studies were conducted in April and November 2003 to provide the first direct measurements of the benthic flux of dissolved mercury species (total and methylated forms) between the bottom sediment and water column at two sampling locations within the southern component of San Francisco Bay, California (hereafter referred to as South Bay): one within the main channel and the other in the western shoal area. Because of interest in the effects of historic mercury mining within watersheds that drain into South Bay, the solutes of primary interest were dissolved-mercury species and the predominant ligands that often control mercury speciation (dissolved sulfide and dissolved organic carbon). Benthic...
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